While previous work has provided a number of regulatory elements useful to affect gene expression in transgenic plants, there is still a great need for novel regulatory elements with beneficial expression characteristics. In particular, there is a need for regulatory elements that are capable of directing expression of transgenes in transgenic crop plants at high levels and in particular tissues, organs, or during specific developmental stages of plant growth.
Useful regulatory elements can be isolated from genes having a desired pattern and/or level of expression of the gene. Silk of certain monocots such as maize plays an important role in many physiologically important processes such as determination of fertilization rate and susceptibility to insects or certain plant diseases. Regulatory elements from genes that are preferentially expressed in plant silk can be utilized for modifying plant phenotypes by expression transgene controlled by such elements. The hydroxyproline rich glycoprotein (HRGP) gene is one of many genes that is preferentially expressed in plant silk (Hood, E., Murphy, J. & Pendleton; Plant Molecular Biology; 23:685-695, 1993 and Raz, R., Cretin, C., Puigdomenech, P. & Martiez-Izquierdo, J.; Plant Molecular Biolgy; 16: 365-367, 1991). Corn and sorghum genes were used for isolating regulatory elements of the present invention to obtain a desired expression pattern of a transgene as presented here.